The specific aims are to: 1) define the role by which cholesterol reduces intestinal fluid secretion in response to bile acids and fatty acids; 2) to relate fluid secretion and generation of c-AMP in response to bile acids and changes in intraluminal pH; 3) to compare the effects of deoxycholate and 3-sulfodeoxycholate on intestinal function in vivo and in vitro; 4) to study the effects of bile acids and fatty acids of liposomes prepared from microvillus membrane lipids of rat and human jejunum; 5) to compare the lipid composition of microvillus membranes in the rat and man; 6) to study the protective role of secretions of the gastrointestinal tract against the effects of dihydroxy bile acids. The overall goal is to define the mechanisms by which bile acids and fatty acids affect intestinal function and the mechanisms by which the intestine is normally protected from any adverse effects of these agents. The experiments involve in vivo perfusion studies in experimental animals, in vitro studies of intestinal transport, morphologic examination of the intestinal mucosa, biochemical analysis of the lipid composition of the microvillus membranes and study of liposomes. The studies will further our understanding of the mechanisms by which bile acids and fatty acids, normally present in the intestine, alter intestinal function and how the intestine is normally protected from these adverse effects. These findings will be applicable to the understanding and possible treatment of such disorders as bile acid and fatty acid diarrhea, bile reflux gastritis and possibly peptic ulcer disease.